Teens' increased freedom to explore different environments potentially increases exposure to contextual risks such as social disorganization. Socially disorganized areas, in which residents have difficulty maintaining social and physical order, are related to increased teen ATOD use/delinquency. Alcohol outlets, indicators of disorganization, influence teen alcohol use through increased access and perceptions of alcohol use as normative. In addition, contextual resources such as collective efficacy, a resource based on social ties among neighbors and their willingness to intervene for the good of the neighborhood may protect against teen risk behavior. Prior studies have not considered context dynamically, instead focusing on a static area, typically administrative units (e.g., census tracts around the teen's home as the area of environmental influence. However, these units may not capture contextual risks/resources where teens spend time, potentially missing a key influence on ATOD use/delinquency. By instead measuring all the places teens spend time, termed here dynamic context, we will address this gap in past research. The aims of the study are to: 1) Test whether teens' dynamic context includes different geographical areas and reflects greater levels of social disorganization and lower levels of collective efficacy than their residential context; 2) Test whether teens' dynamic contexts broaden and shift to areas of greater social disorganization and fewer contextual resources as they progress into older adolescence; and 3) Test whether: a) increases in exposure to social disorganization and decreases in exposure to collective efficacy in the dynamic context contribute independently to increases in ATOD/delinquency throughout adolescence; and b) these changes in exposure in the dynamic context are more predictive of teen risk behaviors than social disorganization/collective efficacy in the residential space, controlling for covariates. 325 14-16 year olds will be tracked for one month over 3 annual waves. GPS-enabled smartphones will be used to measure teen travel patterns to delineate teens' dynamic contexts, and allow measures of disorganization and collective efficacy to be appended to location points, thus quantifying exposure to contextual influences. Using the phones will also allow ecological momentary assessment (EMA) through text-prompted web surveys to assess ATOD use/delinquency to determine how these behaviors assessed in real-time are linked to exposure to disorganization and collective efficacy. The study will build on an ongoing funded grant that provides an existing sampling frame and archival contextual data. The proposed study expands traditional views of contextual influences by using a novel GPS- EMA integrated approach to examine the importance of considering exposures where teens spend time, as these may be more relevant for risk behaviors. This must be understood in order to inform prevention efforts/policy. This study could guide future prevention efforts that use the phones to deliver prevention messages proximal to risk behaviors by identifying precursors of risk behavior through teens' travel patterns.